The pitch links of most helicopters include length adjusters that are centrally located between the ends of the pitch links. These length adjusters can be manipulated to ensure that all of the pitch links on the helicopter are of a similar length, which results in proper in-flight operation, reduce vibration, and enhance rotor performance. Some helicopters include shields, guards, covers, or other equipment that protect the upper control mechanism from rain, snow, and other weather elements.
FIG. 1 is a perspective view of an existing portion of a helicopter 100, including two blades 102, an upper control mechanism 104, and two pitch link assemblies 106. In operation, upper control mechanism 104 (which rotates along with blades 102) actuates pitch link assemblies 106 to adjust the pitch of blades 102. In this regard, upper control mechanism 104 generally raises or lowers pitch link assemblies 106 to cause blades 102 to rotate about their respective longitudinal axes. The arrows 108 in FIG. 1 indicate the rotation of blades 102 about their longitudinal axes.
FIG. 2 is a partial cross sectional view of an existing helicopter blade pitch link assembly and protective boot. FIG. 2 includes a schematic partial cross sectional view of a helicopter 200 having an upper control mechanism 202, a pitch link assembly 204, a canopy 206, and a protective boot 208. The protective boot 208 is formed from a flexible material that enables the upper control mechanism 202 to raise and lower the pitch link assembly 204 without breaking the weather “seal.” In FIG. 2, the protective boot 208 has a lower section 210 that resembles an accordion and an upper section 212 that resembles a sleeve. Lower section 210 is secured to the center of the pitch link assembly 204 using string or laces 214, while upper section 212 is secured near the upper end of pitch link assembly 204 using string or laces 216. These laces 216 are concentrated about the upper end of the tube-shaped portion of protective boot 208. As depicted in FIG. 2, upper section 212 of protective boot 208 covers most of the portion of pitch link assembly 204 located above canopy 206. Pitch link assembly 204 includes an adjustment mechanism 218 that is located under canopy 206 and, consequently, under protective boot 208. To adjust the length of pitch link assembly 204, protective boot 208 must be untied, removed, or disassembled to provide access to the adjustment mechanism 218 of pitch link 204.
FIG. 3 is a top view of a portion of an existing helicopter 300 with the blade 302 slightly misaligned with its pitch axis. For simplicity, only one blade 302 is shown attached to the rotor. As shown in FIG. 3, helicopter 300 accommodates three blades and three respective pitch link assemblies 304 protruding through a canopy 306. Canopy 306 is a rigid cover that extends over the upper control mechanism for the helicopter 300, thus protecting the upper control mechanism from the elements. Canopy 306 includes holes 310 formed therein; the pitch link assemblies 304 protrude through these holes 310. Protective boots 308 encircle the pitch link assemblies 304, and span the spaces between the pitch link assemblies 304 and canopy 306. In other words, protective boots 308 fill the gaps created by the holes 310 that receive the pitch link assemblies 304.
As evidenced by FIG. 2 and FIG. 3, it can be difficult to replace a worn protective boot in the field because the respective pitch link assembly must be fully or partially removed from the upper control or otherwise disassembled to enable a technician to slide the new protective boot over the pitch link assembly.
FIG. 4 is a perspective view of an existing helicopter blade pitch link assembly protective boot 400. This protective boot 400 includes a zipper 402 that partially extends along a sleeve section 404. The upper end 406 and the lower end 408 of protective boot 400 are continuous, i.e., they are not designed to be separable. Accordingly, to replace the protective boot 400, a technician must disconnect the pitch link from the control arm, remove the pitch link assembly entirely out of the protective boot 400, install a new protective boot, and replace the pitch link assembly onto the control arm. Whenever the pitch link assembly is removed in this fashion it requires a post-maintenance test flight to insure that nothing has changed on the helicopter. Such maintenance and testing can be very time consuming, labor intensive, and expensive.
It is desirable to design a new pitch link assembly protective boot that can be easily installed in the field without the need to remove or unlink the pitch link assembly, which also eliminates the need for a post-maintenance test flight. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.